Switchable adhesive and objects utilizing the same

ABSTRACT

A carpet material with at least one of its components made easier for recycle by use of an adhesive which can be selectively altered to change the adhesion strength to allow component carpet layers to be separated.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to United Kingdom No. 0914377.7 filedAug. 17, 2009, herein incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

The current invention relates to a means whereby an object can berendered more readily adaptable from a first form suitable for a firstuse to a second form suitable for a second use, and to an adhesive, inparticular, but not necessarily exclusively, a hot aqueous solventswitchable adhesive comprising or essentially consisting of aplasticized esterified expanded starch obtained by at least expandingstarch to provide an expanded starch, esterification of the expandedstarch to provide an esterified expanded starch, and plasticization ofthe esterified expanded starch to provide a plasticized esterifiedexpanded starch. In particular, the current invention relates to amethod of using such hot aqueous solvent switchable adhesive as theagent for allowing the adaptability of the object to be achieved, andthe use and preparing of such adhesive for use in various objects torender the same more readily recyclable as a result of the adaptability.In particular, the invention is directed towards floor coverings such ascarpet, carpet tiles or rugs with a first form for use as the floorcovering or part thereof and a second form in which at least one of thecomponents of the object is more readily available to be recycled.

Floor coverings are widely used and examples of these are carpet tiles,carpets or rugs (hereinafter referred to in a non limiting manner as“carpets or carpet tiles”). Carpets or carpet tiles are the floorcovering of choice in many households and businesses in the world butunfortunately carpet or carpet tiles have a limited lifespan and musteventually be replaced, with the resultant used carpet waste generallybeing sent to landfill.

These vast quantities of carpet waste have a negative impact on theenvironment, and the recycling of materials, like nylon and bitumen,comprised in the carpet is currently limited. The quantity of usedcarpet or carpet tiles discarded thus amounts to significant economicallosses in potentially reusable materials.

It is therefore not surprising that, in order to limit impact on theenvironment and reuse some of the materials in carpet or carpet tiles,recycling has in recent years become attractive. Recycling carpet orcarpet tiles, however, is difficult because the components that are usedto build up carpet or carpet tiles are chemically and physicallydiverse.

Carpets or carpet tiles, typically comprise a traffic-bearing or wearface surface on a primary backing such as a fibrous face surface(hereinafter referred to as a carpet face layer), which has been woven,needle-punctured, fusion-bonded or otherwise secured to a primarybacking layer or sheet, and a backing layer which includes a surface towhich is bonded one or more layers of solid or foam backing material.

A solid backing material typically comprises thermoplastic-typematerials like a polyvinyl chloride backing material or a bitumen oratactic polypropylene backing layer. For example, carpet or carpet tilescan consist of a carpet face layer of yarn (or carpet fibre), and abacking layer which includes any or any combination of bitumen, EVA(ethylene-vinyl acetate), APP (atactic polypropylene), hot melts,urethanes, and SBR (styrene-butadiene) and/or polypropylene; and anadhesive composition which attaches the filaments of the carpet facelayer (yarn; carpet face fibres) to the backing layer. In addition,other components like a glass backing, or a primary backing fabric maybe present (see FIG. 1).

A widely applied adhesive to bind the filaments within the carpet facelayer together and bind the carpet face layer to for example the bitumenbacking layer of the carpet or carpet tiles is latex, in particularcarboxylated styrene butadiene copolymer latex, also referred to asSBR-latex. Such materials have been used as carpet or carpet tilesbacking adhesives for many years.

To recycle carpet or carpet tiles, the carpet face layer, adhesive andbacking layer should typically be separated from each other in order tobe reprocessed into new products or to be chemically recycled.Unfortunately, recycling of the components of carpets or carpet tilesare hindered due to the residual presence of adhesive, for example SBRlatex, when the layers have been mechanically separated under greattensile stresses. In other words, adhesive might still be present bothin the yarn of the carpet face layer and in/on the backing layer,thereby providing contaminated materials not suitable for proper reuse.

Various methods for better separation of the components of carpet orcarpet tiles have been proposed, either by mechanical means or byadjusting the build-up of the components of the carpet or carpet tiles.For example, U.S. Pat. No. 5,240,530 discloses a method of grindingcarpet and washing in a water bath to allow the various materials of thecarpet to be separated by density. This method will however not solvethe problem of residual presence of the adhesive attached to for examplethe yarn or the backing.

U.S. Pat. No. 5,230,473 describes a method for disintegrating,separating and segregating the base component materials of carpet, whichcomprises loosening and debonding a latex/filler binder system from thesecondary backing by application of pressurized fluids and chemicalsolutions. This method has however the drawback that high amounts ofenergy have to be spent in a process using vast amounts of chemicals,while in addition the problem of residual presence of the adhesive in/onthe yarn/fabric is not solved satisfactory.

U.S. Pat. No. 5,840,773 describes a method of extracting nylon fromcarpet waste by dissolving it in an alcohol-water agent. This methoduses large quantities of organic solvents. Another example is U.S. Pat.No. 5,889,142 which discloses dissolving nylon from carpet in acaprolactam-water mixture.

Another approach is to modify the adhesive, allowing it to be moreeasily separated. Although various modified (latex-based) adhesives forcarpet tiles have been described, in general these are not easilyseparated or removed from carpet fibres.

For example, U.S. Pat. No. 4,191,799 discloses an adhesive prepared froma copolymer of styrene, butadiene, and a carboxylic acid-containingmonomer, combined with an olefin-grafted mineral oil extender; U.S. Pat.No. 3,546,059 discloses an adhesive prepared from styrene, butadiene,vinylidene chloride, and a functional monomer that improves the bondingof the fibres of the composite material.

U.S. Pat. No. 6,610,769 discloses adhesives for use in carpet and thatemploys a copolymer dispersion of styrene, butadiene, and a mixture ofethylenically unsaturated carboxylic acid monomers and latex.

JP 6343542 describes the use of a water-soluble adhesive that can bedecomposed or dissolved when the adhesive is immersed into water or hotwater. Water-soluble adhesives and copolymer emulsion adhesives are usedalone or in combination.

However, none provide a satisfactory solution to the problem discussedabove with respect to efficient recycling of objects such as carpet orcarpet tiles, and none provide a satisfactory adhesive that can besuitably used in a carpet or carpet tiles that can be recycled.

It would thus be advantageous to develop a more environmental-friendlyadhesive suitable for use in, for example, carpets or carpet tiles, thathas long durability, resistance to blistering, has good adhesiveproperties, retains strength when wet, but that can easily be removedwithout use of vast amounts of organic compounds or shear forces orother mechanical and environmentally unfriendly chemical treatments, andallows for the removal and/or separation of a backing layer from thecarpet face fibres and efficient recycling of both the carpet face layerand the backing layer.

SUMMARY OF THE INVENTION

A carpet material with at least one of its components made easier forrecycle by use of an adhesive which can be selectively altered to changethe adhesion strength to allow component carpet layers to be separated.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic showing the composition and layers of the carpetof this invention.

DETAILED DESCRIPTION OF THE INVENTION

It has now surprisingly been found that at least one of the abovementioned problems can be solved by the adhesives, use of saidadhesives, and/or methods for preparing such adhesives as disclosed inthe claims as well as by the surprising benefits obtained by using saidadhesives in combination with objects such as carpet or carpet tiles.

In a first aspect of the invention there is provided an object formedfrom a plurality of components, said object having a first form and asecond form in which at least one of the components of the object aremade more readily available for recycling or disposal wherein the objectincludes an adhesive composition, the condition of which can beselectively altered to allow the change in condition of the object fromthe first to the second form to be achieved.

In one embodiment the first form of the object is for use as a floorcovering or as a part thereof. In particular the object can be carpet ora carpet tile.

In one embodiment the adhesive is a hot aqueous solvent switchableadhesive comprising or essentially consisting of a plasticizedesterified expanded starch.

In one embodiment the change in condition is achieved by causing theadhesive to lose or at least reduce it's adhesion with respect to atleast one component of the object. Typically the reduction in adhesionis sufficient to allow the separation of at least one component from theobject to be more easily achieved.

In addition, the current invention relates to a method of using such hotaqueous solvent switchable adhesive as the agent for allowing theadaptability of the object to be achieved.

In one embodiment said plasticized esterified expanded starch isobtained by at least expanding starch to provide an expanded starch,esterification of the expanded starch to provide an esterified expandedstarch, and plasticization of the esterified expanded starch to providea plasticized esterified expanded starch.

The term “hot aqueous solvent switchable adhesive” refers to an adhesivethat can be treated to lose or at least reduce its adhesive function, bytreatment of an object, for example a carpet or carpet tile, includingsaid adhesive, with a solvent at a temperature allowing the adhesive todissolve or disintegrate, thereby losing or reducing its adhesivefunction within the object.

In practicing the current invention, for example, a hot aqueous solventswitchable adhesive that is applied in a carpet or carpet tiles can beremoved by submerging the same in an aqueous solvent, for example water,at a temperature at for example about 100° C., or by treating the carpetor carpet tile with hot steam, or by other means disclosed herein. Thehot aqueous solvent switchable adhesive according to the inventioncomprises or essentially consists of the plasticized esterified expandedstarch described above.

The starch used as the starting material may be obtained/derived fromany normal source of starch, including corn, potatoes and wheat. Starchnormally comprises two major components, amylose and amylopectin. Theunbranched amylose consists of glucose molecules which are mutuallylinked by means of an alpha-1,4 glycosidic bond, whereas amylopectin isbranched.

The terms “plasticized”, “plasticization”, “plasticity” and“plasticizers” all refer to the characteristic of plasticizers tomodify/increase the plasticity or fluidity of the material to which theyare added, e.g. to soften polymers.

The terms “esterified”, or “esterification” and the like all relate tochemical reactions in which two chemicals form an ester as the reactionproduct.

The term “expanded starch” as used herein refers to its normal meaningin the technical field and denotes a starch that has been treated and,as a consequence of such treatment, shows an increased surface area,porosity and decreased density in comparison to the untreated starch.Surface area can be determined by methods available in the art,preferably as exemplified in the examples.

It has been found that an adhesive according to the invention is inparticular suitable as an adhesive for use in floor coverings, inparticular carpets or carpet tiles or rugs (although the use of theadhesive is not limited to only such use).

The adhesive can show at least one, or any combination, of the followingcharacteristics including good adherence of parts forming an object, forexample a carpet or carpet tile (see examples below); long durability;resistance to blistering; retains strength when wet; can completely andeasily be “switched”, meaning it can be treated, when used as anadhesive in an object, without use of vast amounts of organic compounds,to lose or at least reduce its adhesive function in said object,allowing, without the need of high shear forces or other mechanical andenvironmental unfriendly chemical treatment, to (more) easilydisassemble those components of the object that were (directly orindirectly) adhered to each other by said adhesive; and/or allows forimproved removal and/or separation of a backing layer from the carpetface layer and/or also further disassemble and separation of parts ofsaid layers, and efficient or improved recycling of both the carpet facelayer and the backing layer, in comparison to a non-switchable adhesive.

When the adhesive is for example applied in carpet or carpet tiles, itcan function in locking fibres of the carpet face layer into place, andadhering it to the backing layer (either directly or indirectly via anintermediate layer).

While the adhesive of the invention can be applied to the back of anywoven or non woven carpet or carpet tiles material to secure the baseyarns to for example other yarns of the carpet face layer, as well asthe carpet face layer to the backing layer, it is particularly useful inthe manufacture of piled or tufted carpet or carpet tiles. In tuftedloop or cut pile carpet or carpet tiles, the yarn is inserted orstitched through a primary backing fabric by means of an array ofneedles. The primary backing fabric is typically a nonwoven polyester ora woven polypropylene fabric although other materials can be used. Theyarn is then secured to the primary backing with an adhesive precoat.Another process exists in which the pile surface and backing are formedat the same time by a weaving process. In both these types of carpet orcarpet tiles the yarns are mechanically as well as adhesively attachedto the backing layer. In another type of carpet or carpet tilesconstruction, the pile yarns are cut or looped and positioned to form apile layer which is then secured to the backing layer with adhesive.Carpet or carpet tiles of this type are known as Fusion Bonded.

Carpet tiles typically include a backing layer made up of a plurality oflayers. The construction of these tiles are fairly complex and mayconsist of the carpet face layer of a fibrous, e.g. tufted, primarycloth which has been impregnated with latex to stabilize the tufting,and laminated to, for example, a polypropylene layer by using thebitumen.

For a thorough discussion of the manufacture or carpet tiles or carpetsand especially tufted carpets reference is made to “Carpets And OtherTextile Floor Coverings,” Robinson, 2nd Ed., 1972, Textile Book Service,Division of Bonn Industries Inc., The Trinity Press, London. Please,also, see “Wellington Sears Handbook of Industrial Textiles,” Kaswell,1963, Wellington Sears Co., Inc., New York.

In particular, it has been found that the adhesive of the currentinvention is advantageous when the backing layer comprises (oxidized)bitumen, or polymer-modified bitumen or alternatively when the backinglayer includes PVC. Such materials are frequently used as a backingmaterial in the manufacture of carpet or carpet tiles. The carpet orcarpet tile produced has a fibrous face surface herein after referred toas a carpet face layer in a non limiting manner and a back surfaceintegrally bonded to the bitumen composition or PVC, hereinafterreferred to in a non limiting manner as a backing layer. Typically asecondary backing sheet is secured to the back surface of the bitumen orPVC backing layer.

The carpet face layer can be in the form of or include yarn, carpet facefibre and/or tufts and denote a wide variety of materials that can besuitably used in carpet and carpet tiles and that generally form thecarpet face layer i.e., the cloth that is typically seen and walked on(See FIG. 1).

Non-limitative examples are natural or synthetic organic fibres ormixture thereof, materials like silk, cotton, wool, hair, nylon,acrylics, polyester, polyvinyl chloride, polypropylene fibres and thelike. These materials might contain fire retardants, antistatic agents,bacteriostats, antidegradants, dyes, pigments, optical brighteners, andthe like.

The terms “backing layer” refers to material supporting the carpet facefibres and which material is typically a solid, possibly multilayered,polymeric material serving to provide cushioning and dimensionalstability to the floor covering material, and are typically directly orindirectly connected to for example glass backing (see FIG. 1) and/orcarpet face fibres.

When applied in carpet or carpet tiles and the like, an adhesivecomposition must have high adhesive strength when dried to keep thebacking layer and carpet face layer attached, and must retain sufficientstrength when wet to prevent premature failure of the carpet or carpettiles by separation of the fibres of the carpet face layer from thebacking layer, for example during cleaning.

However, while conventional adhesives for carpet or carpet tilestypically have such dry and wet strengths, they are not easily removedfrom carpet fibres, and typically require extensive chemical ormechanical treatment to be removed. In contrast, the adhesive accordingto the invention can easily be “switched”, meaning it can be treated tolose or at least reduce its adhesive function, without the need oforganic solvents, high shear strength and the like, as will be discussedin detail below.

In a preferred embodiment there is provided an adhesive as describedabove wherein the expanded starch has a surface area of at least 80m2/gram, more preferably at least 100 m²/gram, even more preferably atleast 150 m²/gram, most preferably at least 175 m²/gram.

It has been found that when the surface area of the starch molecules isat least 80 m²/gram, more preferably at least 100 m²/gram, even morepreferably at least 150 m²/gram, most preferably at least 175 m²/gram,an adhesive with advantageous properties within the context of thecurrent invention can be provided.

It has been found that expanded starch with a surface area as mentionedabove can advantageously be used in providing the adhesive according tothe invention. It has been found that lower surface areas provide lessefficient plasticisation and modification as higher surface areas. It isbelieved that esterification is slower and does not achieve the samedegree of substitution (DS). Therefore, the product would not show thesame advantageous properties as a product obtained from a starch with asurface area as described.

As will be understood by the skilled person, this in general impliesthat natural starches require modification by expanding the starch, inthat the surface area is increased, in order to be suitably used inproviding an adhesive according to the invention. The person skilled inthe art knows how to determine the surface area of starch, and ispreferably as described in the examples.

In another preferred embodiment there is provided an adhesive accordingto the invention, wherein the esterified expanded starch has a degree ofsubstitution (DS) of at least 1.2, more preferably at least 1.5, evenmore preferably at least 2.0, most preferably at least 2.4.

The term “degree of substitution (DS)” as used herein refers to itsnormal meaning in the technical field and indicates the average numberof reactive hydroxyl groups replaced by substituent groups per glucoseresidue in a starch derivative. Degree of substitution can be determinedas shown in the examples.

It has been found that when the esterified expanded starch has a degreeof substitution as described above (i.e. has a degree of substitution ofat least 1.2, more preferably at least 1.5, even more preferably atleast 2.0, most preferably at least 2.4) the adhesive according to theinvention is in particular suitable as an “Hot aqueous solventswitchable adhesive”, in particular when applied in carpet or carpettiles.

It is believed that the “degree of substitution” is important forreducing the susceptibility of the material to water. Indeed it has beenfound that the degree of substitution has preferably a value asdescribed above. It has been found that the esterified expanded starchwith a degree of substitution as mentioned above can advantageously beused in providing the adhesive according to the invention.

In another preferred embodiment there is provided an adhesive accordingto the invention, wherein the plasticized esterified expanded starch hasa delamination strength of in the range of about 50 N to about 80 N,preferably in the range of about 55 N to about 75 N, more preferably inthe range of about 65 N to 70 N, as determined by the modifiedBS7399:1991 test described in the examples.

In other words, in another preferred embodiment there is provided anadhesive according to the invention, wherein the plasticized esterifiedexpanded starch has a delamination strength of in the range of about 50N to about 80 N, preferably in the range of about 55 N to about 75 N,more preferably in the range of about 65 N to 70 N, as determined inaccordance with BS7399:1991, but with the modification that thespecimens tested were approximately 5 mm wide and 200 mm long, and theforce to continue the delamination is measured by means of a tensiletester (Testometric Micro 350) at a speed of 100+/−10 mm/min and themean delamination force over the range 50%-75% of the total extension ismeasured. (Instead of the median of peak values over a range 25%-75% ofthe extension).

In another preferred embodiment of the current invention, the esterifiedexpanded starch, as used in obtaining the starch according to theinvention, has a density in the range of from 0.10 gr/cm³ to 0.40gr/cm³, preferably from 0.12 gr/cm³ to 0.25 gr/cm³.

In one embodiment the density is in the range from 0.20 gr/cm³ to 0.30gr/cm³.

The person skilled in the art knows how to determine the density ofstarch. It has been found that the esterified expanded starch with adensity as mentioned above can advantageously be used in providing theadhesive according to the invention.

In addition to the above, the adhesive according to the invention canadvantageously be described/defined by a product-by-process, and is notlimited within the context of the current invention to the manipulationof the recited steps, but only to the structure implied by the steps.

The adhesive according to the present invention in one embodiment isobtainable by:

-   a. providing starch;-   b. subjecting the starch to hot aqueous solvent treatment in order    to gelatinize the starch;-   c. treating the gelatinized starch to induce retrogradation in said    gelatinized starch to obtain expanded starch;-   d. adding non-aqueous water-soluble solvent to precipitate the    expanded starch, substantially separating the precipitated expanded    starch from the solvent and further washing of the expanded starch    with a non-aqueous water-soluble solvent until at least 90 vol. % of    the aqueous solvent added under step b is removed;-   e. suspending the expanded starch in inert water-free organic    solvent, adding a catalyst, adding a fatty acid anhydride and either    -   i. keeping the mixture at a temperature and for a period of time        sufficient to allow the formation of an esterified expanded        starch, or    -   ii. treating the mixture in a micro-wave oven at 100-1000 W and        for a period of 1 to 10 minutes sufficient to allow the        formation of an esterified expanded starch;-   f. adding non-aqueous water-soluble solvent to precipitate the    esterified expanded starch, and drying of the esterified expanded    starch; and-   g. admixing a plasticizer to the esterified expanded starch,    allowing the formation of a plasticized esterified expanded starch.

In one embodiment drying of the obtained expanded starch is performed instep d.

As will be understood by the skilled person the adhesive according tothe invention preferably is comprised of, or consists essentially of theobtained plasticized esterified expanded starch as described by theprocess above.

In a further aspect there is provided a method for preparing a hotaqueous solvent switchable adhesive according to the invention, and asfor example described by the product-by-process above.

The particulars of both the described product-by-process and the methodaccording to the invention are described below.

In general, starch is characterized by low surface areas (<1 m²/gram)and pore volumes (<0.1 cm³/gram) but the structure of starch can beopened up by gelatinization.

The person skilled in the art knows how to induce gelatinization ofstarch. For example, when heat is applied to starch granules suspendedin an aqueous liquid, the starch granules absorb water and swell. Starchmolecules have many hydroxyl-groups which can interact with the watermolecules, attracting and holding them. The smaller amylose moleculesdiffuse out of the swollen starch granule and form a 3-D network whichtraps additional water. In other words, starch gelatinization is aprocess that breaks down the intermolecular bonds of starch molecules inthe presence of water and temperature and allows the hydrogen bondingsites (the hydroxyl hydrogen and oxygen) to engage more water.

It has been found that in the process for providing the adhesiveaccording to the invention, preferably the starch is treated by heatingin an aqueous solvent, like water, at a temperature of about 50° C. to200° C., more preferably of from 70° C. to 160° C., even more preferablyof from 90° C. to 130° C. As a consequence of such treatment, the starchgranules first swell and then collapse to form a gel (this is generallycharacterized by an increase in viscosity and at the moment of collapse,a decrease in viscosity).

As discussed above, it has been found that in order to provide for theadhesive according to the invention, a surface area of at least 80m²/gram, more preferably at least 100 m²/gram, even more preferably atleast 150 m²/gram, most preferably at least 175 m²/gram starch (dry) atthis stage in obtaining the adhesive is preferred.

It has appeared preferable that after heat treatment of the starch toinduce gelatinization of the starch, the starch is further treated toinduce retrogradation, for example by storing at low temperature (seebelow). The time necessary to achieve the necessary retrogradationdepends on the type of material used and is typically between two andthree weeks for normal corn starch or one day for high amylose-contentcorn starch.

For example, corn starch heated to 110° C. for 3 hours achieved asurface area after retrograding for 3 weeks at 5° C. of 150-160 m²g⁻¹.High amylose corn starch heated to 120-130° C. in a pressure cooker for1 hour 30 minutes achieved a surface area after retrograding for 2 daysat 5° C. of 180-250 m²g⁻¹.

Retrogradation denotes that dissolved starch transposes from anamorphous state to an insoluble, aggregated, semi-crystalline state. Itis believed the retrogradation takes place as molecular reassociation ofthe hydrated and dispersed starch molecules, presumably through hydrogenbonding. The retrogradation appears in particular to occur in theamylase molecules.

It has been found that, preferably, this retrogradation can be achievedby, for example, keeping the gel at low temperatures (e.g. 5° C.). Morepreferably retrogradation is induced by storing the hot aqueous solventtreated starch at a temperature below 25° C., preferably below 10° C.,more preferably below 5° C., but above −5° C., for at least 10 hours,preferably at least 24 hours, more preferably at least 100 hours, morepreferably at least 500 hours.

Next, it has been found that in order to provide for the adhesiveaccording to the invention, it is most preferred that the aqueoussolvent used for the heat-treatment to induce gelatinization of thestarch as described above, is removed from the starch. Keepingsubstantial amounts of, for example, water present in the starch mixturehas been found to reduce, or even destroy, for example, the surface areaof the starch, and thereby does not allow or not satisfactorily providefor the adhesive of the current invention.

In other words, it has been found that in order to obtain an adhesiveaccording to the invention it is preferable that care is taken thatsubstantially all water (>90%) of the aqueous solvent used to inducegelatinization is removed. It has been found that presence of too muchwater in the starch during subsequent steps in obtaining the starchaccording to the invention, causes the structure of the expanded starchto disintegrate, not providing the optimal adhesive.

In order to remove said aqueous solvent, starch can first beprecipitated by the addition of a compound capable of precipitating thestarch (for example a simple alcohol), after which the aqueous solventcan be separated from the starch.

It will be clear for the skilled person that additional repeating ofsteps to remove aqueous solvent might be required, for example, at least2, 3, 4 or 5 times.

Moreover, it is important to note that the compound used to precipitatethe starch (and/or to remove the aqueous solvent) is inert towards the(expanded) starch and does not, or substantially not, modify itsimportant characteristics for the current invention, for example itshould not or, not substantially, reduce the surface area of the starch.

The removal of (excess) aqueous solvent, like water, from the starch ispreferably achieved by washing steps with a non-aqueous water-solublesolvent, for example a suitable alcohol, also used (or usable) toprecipitate the starch.

Preferably, the non-aqueous water-soluble solvent allowing the starch toprecipitate is selected from the group consisting of methanol, ethanol,propanol, and butanol.

The role of the non-aqueous water-soluble solvent, for example asuitable alcohol like ethanol, is to remove water from the gel withoutcollapsing the pore structure and/or substantially modifying the surfacearea of the expanded starch. It has been found that this preferablyrequires a liquid which is miscible with water but has a lower surfacetension. Such non-aqueous water-soluble solvents, for example an alcohollike ethanol, have the advantage that it is miscible with water, therebyallowing efficient removal of water from the mixture by simple removalof the solvent. In addition, the alcohol does not, or at most onlyminimally interferes with the starch, thereby causing unwantedmodification of the properties of the starch. Moreover, when anon-aqueous water-soluble solvent with low boiling temperature isemployed, it allows for easily drying of the starch afterwards.

It has been found that in particular ethanol is effective for thispurpose although other alcohols give similar if smaller effects. Asalready mentioned above, in a next step, and after removal of excessaqueous solvent, the expanded starch is preferably dried, for example byvacuum drying. This might be done for example under a nitrogen stream.

In another preferred embodiment the non-aqueous water-soluble solventadded under step d) is in a ratio of from 1 volume non-aqueouswater-soluble solvent to 5 volumes aqueous solvent added in step b) to 5volume non-aqueous water-soluble solvent to 1 volume hot aqueous solventadded in step b).

In other words, preferably, the non-aqueous water-soluble solvent isadded in a ratio of from 1 volume non-aqueous water-soluble solvent to 5volumes of the aqueous solvent used in gelatinization of the starch to 5volume non-aqueous water-soluble solvent to 1 volume aqueous solventused in gelatinization of the starch by the hot aqueous solventtreatment.

By applying the above-mentioned volume ratios efficient precipitation ofthe starch is achieved, while in addition, efficient removal of theaqueous solvent is achieved. The person skilled in the art willunderstand that the current invention is not limited to using one andthe same non-aqueous water-soluble solvent, in case further washingsteps are performed, but that, although not particularly preferreddifferent non-aqueous water-soluble solvents of mixtures thereof mightbe employed.

It has, in addition, been found that in a further preferred embodiment,a suitable adhesive according to the invention is obtainable when afterthe further washing of the precipitated starch the precipitated starchis at least once washed with the inert water-free organic solvent ofstep e), and omitting the drying of the obtained expanded starch.

It has surprisingly been found that by at least once washing with thewater-free organic solvent also to be used for subsequent esterificationof the expanded starch, there is limited need for drying of the obtainedexpanded starch, thereby limiting the time required to obtain theadhesive according to the invention.

Preferably, either in the embodiment described above, omitting thedrying step, or in the other embodiments disclosed herein, including thedrying step, the inert water-free organic solvent is selected from thegroup consisting of toluene, benzene, and xylene etc.

It has been found that in particular the use of these inert water-freeorganic solvents is particularly effective. The person skilled in theart understands that water-free is to be construed as describing anorganic solvent not comprising more than 1 w/w % of water, preferably nomore than 0.5 w/w % water, preferably free of water.

It has been found that at this stage in obtaining the adhesive accordingto the invention, or in practising a method according to the inventionthere is preferably provided an expanded starch formed, using a veryrepeatable process, having a surface of at least 80 m²/gram, morepreferably at least 100 m²/gram, even more preferably at least 150m²/gram, most preferably at least 175 m²/gram.

For example, the surface area of the expanded starch is in the range offrom 130 m²/gram to 270 m²/gram, preferably from 140 m²/gram to 260m²/gram, more preferably from 175 m²/gram to 205 m²/gram.

In order to provide for the adhesive according to the invention, theobtained expanded starch most preferably is further modified, forexample and preferably by esterification, and maybe other modifiers. Ithas been found that if such modification is not performed, an adhesiveaccording to the invention, and suitable for the use according to theinvention, is more difficult to obtain.

The person skilled in the art knows how esterification of starch can beachieved, and is for example described in various patents and scientificpublications (see for example Kirk-Othmer, Encyclopedia of ChemicalTechnology, 1997, 4th edition, Vol. 22, p. 699-719 and Ullmann'sEncyclopedia of Industrial Chemistry, Vol. A25, 1994, p. 1-18.)

For example, low DS (˜0.5) acetylated starch can be prepared in a systememploying acetic anhydride-aqueous alkali at pH 7-11 and roomtemperature. This method can only be employed when preparing lightlysubstituted acetylated starches, however. Starch granules treated withacetic anhydride alone at 20° C. for 5 months will not, it is believed,result in any reaction. At room temperature, pyridine treatment rendersthe starch granule reactive, though.

Treatment of starch with acid anhydride in DMSO (dimethyl sulfoxide)requires triethylamine as a catalyst and acid scavenger. With thismethod, starch derivatives of acetic, propanoic, and butanoic anhydrideshave been prepared up to DS of 0.08.

When employing glacial acetic acid alone at 100° C. for 5-13 h, theesterification gives a product with 3-6% acetyl groups. Treatment ofstarch with concentrated formic acid leads to gelatinization andsimultaneous esterification. Acetylation with ketene produces starchwith an acetyl content of 2.2-9.4%. The reaction is usually conducted inacetic acid, diethyl ether or acetone with an acid catalyst.

Also vinyl acetate has been employed in the acetylation. A methodcomprising reacting starch in the presence of an alkaline catalyst, suchas an alkali metal carbonate or hydroxide, ammonium hydroxide or analiphatic amine, and more than 10% water by weight of dry starch with anester of a carboxylic acid and an ethylenically unsaturated alcohol,such as vinyl acetate can be used.

U.S. Pat. No. 2,461,139 discloses another method for preparing starchesters. The method includes reacting starch and water with an organicacid anhydride and maintaining the pH of the reaction in the alkalinerange between 7 and 11. The organic acid anhydrides include aceticanhydride, propionic anhydride, phthalic anhydride and butyricanhydride. Typically, starch is suspended in water at 25° C. and sodiumhydroxide is added to raise the pH to about 10. Then enough aceticanhydride is added to the suspension to lower the pH to about 7 followedby separating the starch ester by filtration.

From the above, it is clear that many methods for performingesterification of starch have been described. Besides realizing that inorder to obtain the adhesive according to the invention it is muchpreferred, if not necessary to modify an expanded starch by for exampleesterification, in addition it has also surprisingly been found that themethod applied for esterification appears critical.

It has been found that for obtaining the adhesive of the currentinvention esterification of the (expanded) starch can not be carried outby just any of the available methods for esterification.

For example, it has appeared that methods providing (expanded) starcheswith a DS of less than 1.0 does not sufficiently allow to obtain asuitable adhesive of the current invention.

Furthermore, performing the esterification in relative aqueousconditions also does not allow for obtaining the adhesive according tothe invention.

The use of particular catalysts like pyridine or NaOH (50% w/w inaqueous solvent) at this stage does also appear not to provide for anadhesive according to the invention. As the skilled person willunderstand, some less aggressive catalyst may also catalyse the reactionmaintaining the surface area to some degree.

It was thus established after intensive experimentation that in order toprovide an adhesive of the invention it is highly advantageous thatcatalyst, solvent and reagent, i.e. the compounds used in esterificationof the expanded starch to provide the esterified (expanded) starch mustbe substantially inert (besides providing for esterification of thestarch) towards the obtained expanded starch, and as described above.

These compounds should therefore not, or substantially not, interactwith the expanded starch and thereby substantially modify for examplethe surface area of the expanded starch. It has been found thatparticular compounds might dramatically influence the surface area ofthe expanded starch and thereby do not allow to provide the adhesiveaccording to the invention.

Therefore, it has surprisingly been found that in order to obtainadhesive according to the current invention, esterification ispreferably performed by using an inert water-free organic solvent thatis selected from the group consisting of toluene, benzene, and xyleneetc. In particular toluene is preferred, as it provides good results inperforming the invention. The person skilled in the art knows how toperform esterification, for example as shown in the Examples herein.

In another preferred embodiment, the catalyst is selected from the groupconsisting of amines, dimethylaminopyridine (DMAP), triethylamine, andpyridine, most preferably the catalyst is DMAP. In particular thesecatalysts have been found to efficiently enhance esterification, whereasothers, for example acid catalysts like H2SO4, are less preferable.

Preferably, in obtaining the adhesive according to the invention, afatty acid anhydride is used as the reagent, i.e. as the compound usedto react with the expanded starch to provide the esterified starch.Preferably the fatty acid anhydride is from C2 fatty acid anhydride toC12 fatty acid anhydride, or mixtures thereof, preferably from C2 fattyacid anhydride to C6 fatty acid anhydride, most preferably the fattyacid anhydride is acetic anhydride.

Other examples of such monocarboxylic fatty acid anhydrides containing2-7 carbon atoms, and suitable in the current invention, are aceticacid, mono-, di- or tri-chloracetic acid, mercaptoacetic acid, propionicacid, 2-hydroxy-propionic acid, 2-chloropropionic acid, acrylic acid,2-bromo-2-methyl propionic acid, methacrylic acid, 2,2-dimethylpropionic acid, butyric acid, isobutyric acid and crotonic acid.

In another preferred embodiment, in order to provide the adhesiveaccording to the invention, the esterified expanded starch, obtainableas described above is admixed with a suitable plasticizer allowing theformation of a plasticized esterified expanded starch according to theinvention.

For the first time it has been found that such plasticized esterifiedexpanded starch obtainable by the steps described herein, acts as anadhesive that can be used as a hot aqueous solvent switchable adhesive.

It has been found that the plasticizer applied is preferable selectedfrom the group consisting of phthalate esters, dimethyl- anddiethylsuccinate, glycerol triacetate (triacetin), glycerol mono- anddiacetate, glycerol mono-, di- and tripropionate, glycerol tributanoate(tributyrin), glycerol mono- and dibutanoate, glycerol mono-, di- andtristearate, and other related glycerol esters, lactic acid esters,citric acid esters, adipic acid esters, stearic acid esters, oleic acidesters, ricinoleic acid esters, other fatty acid esters, glycerol,polycaprolactone, glyceryltrioleate, preferably the plasticizer isglycerol or glycerol triacetate, most preferably the plasticizer isglycerol triacetate.

Preferably, the plasticizer is admixed in an amount from 10 to 40%,preferably from 15 to 35%, more preferably from 20 to 30% by weightbased on the esterified expanded starch. This has been shown to inparticular allow for providing an adhesive according to the invention.

In another embodiment of the current invention, esterification isperformed by keeping the mixture comprising expanded starch, inertwater-free organic solvent, catalyst, and a fatty-acid anhydride at atemperature below the boiling point of the inert water-free organicsolvent in the range of from 30° C. to 130° C., more preferably from 50°C. to 105° C., most preferably from 70° C. to 100° C.

The adhesive or esterified expanded starch according to the inventioncan advantageously be admixed with flame-retardants, fillers,preservatives, binders, antimicrobial agents, commonly applied in theart, in particular when the adhesive or esterified expanded starchaccording to the invention is applied as an adhesive in carpet or carpettiles and the like. Examples of such materials include aluminatrihydrate, zinc borate, calcium carbonate, china clay and conductivecarbon black.

As will be understood by the skilled person it might be advantageous toadmix particular compounds to the adhesive, for exampleflame-retardants, fillers, preservatives, binders, antimicrobial agentscan be admixed to the esterified expanded starch, or to the plasticizedesterified expanded starch, or at any procedural step in the formationof the adhesive according to the invention, as long as the addition inthe end does not substantially negatively change the adhesive withrespect to for example its use as an adhesive, for example in carpet orcarpet tiles and as described herein.

It has thus been found that the adhesive described herein and obtainableby the various methods described herein is an environmental-friendlyadhesive suitable for use in carpets or carpet tiles, that can have longdurability, resistance to blistering, good adhesive properties, retainsstrength when wet, but that can almost completely and easily be removedwithout the use of vast amounts of organic compounds or shear forces orother mechanical and environmental unfriendly chemical treatments, andallows for the removal and/or separation of a backing layer from thecarpet fabric (or yarn) and efficient recycling of both the carpet facelayer and the backing layer.

According to another aspect of the invention, there is thus provided theuse of an adhesive according to the invention, for example obtainable asdescribed herein, as a hot aqueous solvent removable adhesive.

It has been found that it can be advantageously applied in particular tofloor coverings such as carpet or carpet tiles or rugs.

The use of the adhesive according to the invention now for the firsttime allows for efficient and environmental methods for recyclingobjects wherein such adhesive is applied, and in preparing suchrecyclable objects.

Therefore, in another aspect according to the current invention, thereis provided a method of preparing a recyclable carpet or carpet tilecomprising the steps of providing a carpet face layer, providing abacking layer, contacting the adhesive according to the invention withthe carpet face layer and the backing layer thereby adhering the carpetface layer to the backing layer with the adhesive.

Also provided is a method for recycling components of carpet or carpettiles comprising the steps of providing a recyclable carpet or carpettile obtained as described above and optionally reducing the size of therecyclable carpet or carpet tile; treating the recyclable carpet orcarpet tile with an hot aqueous solution preferably, at least 20° C.,preferably, at least 30° C., preferably, at least 70° C., morepreferably, at least 90° C., i.e. at room temperature or above, orsteam, for a period of time sufficient to allow the hot aqueous solventremovable adhesive to (substantially) detach (or de-adhere); andseparating the carpet face layer from the carpet backing layer. Mostpreferably steam is used.

It will be understood by the skilled person that a floor covering, suchas a carpet or carpet tile, that at least comprises a carpet face layer,a backing layer, and an adhesive according to the invention and whichadhesive directly or indirectly adheres the carpet face layer to thebacking layer has advantageous properties. Directly or indirectly is tobe construed as indicating that the carpet face layer might be directlyadhered to the backing layer by the adhesive, i.e. without anyadditional intermediate layer, or indirectly, i.e. with/via anadditional intermediate layer.

It has further surprisingly been found that the adhesive according tothe invention has in particular good flame retardant properties.Therefore, in a preferred embodiment, the adhesive according to theinvention is used as a flame retardant. The use of the adhesive as aflame retardant can be in addition to the provision of the adhesive as ameans to allow the form of the object to change to be more easilyrecyclable but it should also be appreciated that it is another aspectof the invention that the use of the adhesive as herein described withan object in which the form of the object is not required to be changedis another aspect of the invention inasmuch that there is provided anobject which is provided with flame retardant properties as a result ofthe use of the adhesive in accordance with the invention.

FIG. 1 shows a schematic representation of a typical build-up of acarpet or carpet tile in which there is provided a backing layercomprising a polypropylene layer 2 with backing layers 4, 6, possibly ofbitumen, and with glass backing layers 8, 10 intermediate thereof. Aprimary backing fabric 12 is provided which interfaces with the yarn 14to form the carpet face layer. An adhesive 16 in accordance with theinvention is provided which engages the yarn and primary backing fibretogether and with the backing layer. The adhesive is provided to becapable of being changed in condition so as to allow the carpet orcarpet tile to be changed from the form shown in which the same is usedas a floor covering, to a second form in which at least one of thecomponents, and/or parts of the components can be rendered more easilyseparable for recycling purposes.

Examples of the generation of the adhesive and use of the same inaccordance with the invention are now described with reference to thefollowing examples.

Example 1 1.1 Gelatinization

Cornstarch 75 g (27% w/w amylose, 73% w/w amylopectin) 0.463 mol wasadded to 1.5 L of distilled water in a 2 L round-bottom flask. Themixture was then gelatinized in an oil bath at 110° C. with continuousstirring for 3 hours. As the person skilled in the art will understandgelatinization conditions will depend on the starch type. High amylose(70% amylose) cornstarch for example will preferably be performed at ahigher temperature (˜140° C.).

1.2 Retrogradation

Gelatinized cornstarch prepared in 1.1 was poured into 4×500 ml powderglass jars. While still hot, lids were attached forming a barrieragainst microbial activity. Samples were then labelled and placed in afridge at 5° C. for 3 weeks. As the person skilled in the art willunderstand, also retrogradation stage depends on the starch type. Highamylose (e.g. 70% amylose) cornstarch for example will retrogradesufficiently after only one or two days, as already described above.

1.3 Solvent Exchange A.

Retrograded starch gel as obtained under 1.2, 1.5 L, 75 g was mixed for15 minutes with 1 L of ethanol using an overhead stirrer (Heidolph 2050RZR electronic). The mixture was then left to settle, and the separatedsolvent decanted off and replaced with a fresh 1 L batch of ethanol.This process was repeated five times. Water free expanded starch wasthen placed in a vacuum oven set at 50° C. for 12 hours.

B.

As above, but wherein the last solvent exchange was with toluene insteadof ethanol and in this case it was found that the drying step could bereduced or avoided altogether.

1.4 Esterification A.

5 g (30.9 mmol) expanded starch, as obtained under 1.1-1.3, with asurface area of more than 160 m²/g was added to a 100 ml two-neckedround bottom flask. To this, 70 ml toluene was added, followed by 4.37mls, 4.73 g (46.3 mmol) acetic anhydride (Aldrich). The mixture washeated to 90° C. and stirred for 5 minutes; after which 0.2 g (1.64mmol) 4-(dimethylamino) pyridine (DMAP) was added. The reaction wasmaintained at 90° C. while stirring for 12 hours. Once completed themixture was cooled to 20° C. and 50 mls of ethanol added. Theprecipitate formed was stirred for two minutes, filtered, and washed andfiltered a further 4 times. The product was dried at 40° C. for 24 hoursunder reduced pressure.

B.

As under A, with the only difference that the reaction was notmaintained at 90° C. while stirring for 12 hours, but maintained in amicrowave at 300 Watt for a period of 1-10 minutes (in this case 5minutes).

1.5 Precipitation

The esterified expanded starch obtained above was precipitated by adding1 volume of ethanol to the mixture.

1.6 Plasticizing

A 25% plasticized esterified expanded starch mix was prepared byweighing out 75 grams of the esterified expanded starch as obtainedabove into a large beaker (in case ATH as a flame retardant is tested,an additional 75 grams of ATH (alumina trihydrate) was added to theesterified expanded starch. Next, 25 grams glyceryl triacetate wasweighed out into a small beaker and carefully added to the esterifiedexpanded starch, while mixing with a spatula until uniformly dispersed.The mixture was then mixed in a 1 litre metal tin with acetone (up to atotal volume of approximately 800 ml) and stirred in a Silverson HSmixer, while moving the tin to ensure uniform mixing. The mixture wasstirred until a uniform paste consistency was produced.

Example 2 2.1 Determination of Surface Area of Starch.

Nitrogen adsorption/desorption measurements of the starches wasundertaken on a Micromeritics ASAP 2010 instrument at 77K withapproximately 0.1 g of material. Prior to analysis, all samples wereout-gassed for a minimum of 3 hours at 65° C. and corrected for massdifferences after the experiment. Surface areas were calculated usingthe BET equation.

2.2 Determination of Starch Esterification—Titration Method.

Titration is the methodology that is most accepted in the field. Therepeating unit of starch (α-D-glucopyranose) has three hydroxyl groups;therefore the maximum degree of substitution (D.S.) for starch isusually quoted as being three. However, the D.S. could exceed three asend units can have four ester-groups, for example acetyl groups,attached. The titration method employed to determine the DS of theesterified (expanded) starch was based on the procedure employed byWurzburg (Wurzburg, O., (Ed. Whistler, R.), Methods in carbohydrateschemistry, IV, Academic press, London, (1964), p288.) For example,acetylated starch (1.0 g) was placed in a 250 ml flask and 50 ml of 75%ethanol in distilled water was added. The loosely stoppered flask wasagitated, warmed to 50° C. for 30 min, cooled, and 40 ml of 0.5M KOHadded. The mixture was left for 72 hours with occasional stirring.Excess alkali was back-titrated with 0.5M HCl using phenolphthalein asan indicator, after which it was left for a further 2 hours, and anyadditional alkali which may have leached from the sample titrated. Ablank using the original unmodified starch was also tested. Acetylcontent (Acetyl %) was calculated according to equation below:

${{Acetyl}\mspace{14mu} \%} = \frac{( {\lbrack {{{Blank}\mspace{14mu} ( {cm}^{3} )} - {{Sample}\mspace{14mu} ( {cm}^{3} )}} \rbrack^{\prime}\mspace{14mu} {Molarity}\mspace{14mu} {of}\mspace{14mu} {HCl}^{\prime}\mspace{20mu} 0.0473^{\prime}\mspace{14mu} 100} }{{Sample}\mspace{14mu} {Weight}\mspace{14mu} (g)}$

Blank and sample titration volumes in ml, sample weight was in g. DS isdefined as the average number of sites per glucose unit that possess asubstituent group (See Singh, N., Chawla, D., Singh, J., Food Chem., 86,(2004), 601-608; Whistler, R., Methods in Carbohydrate chemistry:Starch, Vol. IV, Academic Press, London, (1964); Elomaa, M.,Carbohydrate Polymers, 57, (2004), 261-267). Acetyl % was used tocalculate the D.S. according to the following equation:

${D.\; S.} = \frac{( {163^{\prime}\mspace{14mu} {Acetyl}\mspace{11mu} \%} )}{( {4300 - \lbrack {42^{\prime}\mspace{14mu} {Acetyl}\mspace{14mu} \%} \rbrack} )}$

2.3 Determination of Starch Esterification—Thermogravimetric Method

TG analysis of hydrolysed starch was carried out on a Seiko™ instrumentsInc. SII Exstar 6000™, TG/DTA 6300™ using approximately 15 mg ofmaterial weighed in to a platinum sample pan. An empty platinum pan wasused as reference. The sample was then heated using the followingprogram:

20 to 400° C. at 10° C. minute⁻¹; hold for 1 minute.

The decomposition temperature was taken as the peak temperature from thedTG profile.

This value was then correlated against the D.S. value obtain for theparticular acetylated starch tested according to the methodologydescribed in 2.2.

2.4 Determination of Lamination Strength: a Modified BS7399 Test A.Methodology for Lamination of Starch Precoated Topcloth to Pre-CastBitumen

The starch precoated topcloth was prepared by using a doctor blade, setat a 2-3 mm gap to apply a smooth layer of plasticized esterifiedexpanded starch as obtained above to Aiki Kamala topcloth Immediatelyafter application, release paper was applied and the sample was rolledwith a heavy roller (5200 gram, with a length of 38 cm and a diameter of45 mm), as described below, in order to ensure good penetration into thebackstitch. With the doctor blade set at the same gap, a second layerplasticized esterified expanded starch was applied. Afterwards thesample was dried in an oven at 70° C.

By introducing silicon-coated release paper between the topcloth andbitumen on the Bitumen Backing Line, a sample of pre-cast bitumen can beobtained, without any adhered topcloth. This will be a consistent 3150gm⁻² of bitumen, extruded around two layers of glass fleece, with apolypropylene fibre backing.

Next, the pre-cast bitumen is heated (exposed bitumen towards the heatsource, and fibre backing away) under infra-red until the bitumen startsto melt (approximately 180° C.-200° C.).

Whilst the bitumen is still molten, the starch precoated topcloth sampleis laid on top of it (precoated side to molten bitumen), and a steelroller is used to apply pressure to the combined sample to aidconsistent lamination. The roller used is 5200 gram, a length of 38 cmand a diameter of 45 mm, and is rolled four times over the sample. Thesample is then rotated through 90° and the roller is used to applypressure a further four times.

The sample is left to cool at ambient temperatures for 15 minutes beforebeing trimmed down on the hydraulic press and die-cutter, to remove atleast the outer centimetre of the precoated sample, where laminationpressures are inconsistent.

The laminated sample is then left to condition at 65+/−2% RH, 20+/−2°C., for 24 hours prior to testing.

Sample size for tensile testing is 40 mm×200 mm

B. Delamination Force BS7399:1991

The delamination force is determined in accordance with British Standard7399:1991, included herewith by reference, but with the followingmodifications:

The specimens tested were approximately 40 mm wide and 200 mm long, andthe force to continue the delamination is measured by means of a tensiletester (Testometric Micro 350) at a speed of 100+/−10 mm/min The testalso differs from BS7399 in that the mean delamination force over therange 50%-75% of the total extension is measured in place of the medianof peak values over a range 25%-75% of the extension.

2.5 Switchability (Modified BS7399;1991)

Switchability is determined by repeating the measurement under 2.4 Babove (Delamination Force BS7399:1991) on duplicate specimens but afterimmersion of the sample in boiling water for 2 minutes followed byblotting to remove excess water immediately before measuring. Thedifferences between the 2 sets of delamination values indicates thedegree of switchability.

2.6. Other Tests

In addition to the above measurements, loop anchorage (in accordancewith BS5229:1981); Martindale (in accordance with DD ISO/PAS11856:2003),Castor chair (in accordance with EN985:1994), Hexapod (in accordancewith ISO/TR10631:2000), Dimensional Stability (in accordance withISO2551/EN986:2005), and Flammability (in accordance withISO9329/1:1997) were measured.

3. Experimental Outcome

3.1

The starch as treated as described in detail under Example 1 wasanalyzed with the methods described under Example 2. Results as obtainedare given in the tables below. It was found that applying either one ofthe two methods of solvent exchange as described under Example 1.3and/or the two methods for esterification described under Example 1.4did not substantially influence the properties of the plasticizedesterified expanded starch obtained.

TABLE 1 Test Results/Grade Pass/fail Comments Surface area ofexpanded >160 m2 starch Degree of substitution of >2.5 esterifiedexpanded starch Density of esterified 0.2 to 0.3 g cm−3 expanded starchLoop anchorage 28 N Martindale 2 Pass Castor chair R value = 2.6 PassGood grade, >2.4 is suitable for intense use Hexapod S 3 3/4; L 2 3/4;Class 31 Dimensional stability L 0.04% W Excellent 0.05% Flammabilitywithout ATH: Pass Excellent BL (mm) 130 CRF (KWm-2) 10.4 Smoke (%) 49.9with ATH: BL (mm) 110 CRF (KWm-2) 10.5 Smoke (%) 67.8 (BL = burn length;CRF = Critical radiant flux) Delamination strength 60 N PassDelamination strength 30 N Pass Lamination strength is reduced afterimmersion in water at 100° C. for 2 minutes (switchability) followingtreatment with hot water3.2

Plasticized esterified expanded starch is prepared as described above,with the modification that different types of starch are used. Theresults show that when different types of starch were treated to obtainplasticized esterified expanded starch as described herein, there can beprovided hot aqueous solvent switchable adhesives according to theinvention, suitable for use as adhesive in the preparation of floorcovers, in particular carpet or carpet tiles.

Although corn starch and high amylose corn starch are described above,all starch sources are possible for use in obtaining an adhesiveaccording to the invention. Preferable are those starches with a greateramylose content.

1. An object formed from a plurality of components, said object having afirst form and a second form in which at least one of the components ofthe object are made more readily available for recycling or disposal,wherein the object includes an adhesive composition, the condition ofwhich can be selectively altered to allow the change in condition of theobject from the first to the second form to be achieved.
 2. An objectaccording to claim 1 wherein in the first form the object is for use asa floor covering or as a part thereof.
 3. An object according to claim 2wherein the object is a carpet or carpet tile.
 4. An object according toclaim 2 wherein the object includes a carpet face layer and a backinglayer and the adhesive directly or indirectly adheres the carpet facelayer to the backing layer.
 5. An object according to claim 1 whereinthe adhesive acts as a flame retardant.
 6. An object according to claim1 wherein a plurality of components are separable from the objectfollowing the change in condition of said adhesive composition.
 7. Anobject according to claim 1 wherein the change in condition of theadhesive composition is achieved by performing a treatment or operationon the said object
 8. An object according to claim 1 wherein the changein condition of the adhesive composition is such that the adhesionbetween the components with which the adhesive is in contact is reduced.9. An object according to claim 1 wherein the adhesive composition is ahot aqueous solvent switchable adhesive comprising or essentiallyconsisting of a plasticized esterified expanded starch.
 10. An objectaccording to claim 9 wherein said plasticized esterified expanded starchis obtained by at least expanding starch to provide an expanded starch,esterification of the expanded starch to provide an esterified expandedstarch, and plasticization of the esterified expanded starch to providea plasticized esterified expanded starch.
 11. A carpet or carpet tileincluding an adhesive composition, the condition of which can be changedto allow separation of at least one component of the carpet or carpettile.
 12. A carpet or carpet tile according to claim 11 wherein the atleast one component is removed when the carpet or carpet tile, is nolonger in use.
 13. A carpet or carpet tile according to claim 11 whereina plurality of components are separable from the carpet or carpet tilefollowing the change in condition of said adhesive composition.
 14. Acarpet or carpet tile according to any of the claim 11 wherein thechange in condition is achieved by performing a treatment or operationon the carpet or carpet tile.
 15. A carpet or carpet tile according toclaim 11 which is rendered recyclable by the change in condition of theadhesive composition included therein.
 16. A carpet or carpet tileaccording to claim 11 wherein the adhesive composition whose conditionis changed is that which allows the backing layer of the carpet orcarpet tile to be attached to the carpet face layer.
 17. Hot aqueoussolvent switchable adhesive comprising or essentially consisting of aplasticized esterified expanded starch characterized in that saidplasticized esterified expanded starch is obtained by at least expandingstarch to provide an expanded starch, esterification of the expandedstarch to provide an esterified expanded starch, and plasticization ofthe esterified expanded starch to provide a plasticized esterifiedexpanded starch.
 18. Adhesive according to claim 17, wherein theexpanded starch has a surface area of at least 80 m²/gram, morepreferably at least 100 m²/gram, even more preferably at least 150m²/gram, most preferably at least 175 m²/gram.
 19. Adhesive according toclaim 17, wherein the esterified expanded starch has a degree ofsubstitution of at least 1.2, more preferably at least 1.5, even morepreferably at least 2.0, most preferably at least 2.4.
 20. Adhesiveaccording to claim 17, wherein the plasticized esterified expandedstarch has a delamination strength of in the range of about 50 N toabout 80 N, preferably in the range of about 55 N to about 75 N, morepreferably in the range of about 65 N to 70 N, as determined inaccordance with BS7399:1991, but with the modification that thespecimens tested were 40 mm wide and 200 mm long, and the force tocontinue the delamination is measured by means of a tensile tester at aspeed of 100+/−10 mm/min and the mean delamination force over the range50%-75% of the total extension is measured.
 21. Adhesive according toclaim 17 wherein the esterified expanded starch has a density in therange of from 0.10 gr/cm³ to 0.40 gr/cm³.
 22. Adhesive according toclaim 17 obtainable by a. providing starch; b. subjecting the starch tohot aqueous solvent treatment in order to gelatinize the starch; c.treating the gelatinized starch to induce retrogradation in saidgelatinized starch to obtain expanded starch; d. adding non-aqueouswater-soluble solvent to precipitate the expanded starch, substantiallyseparating the precipitated expanded starch from the solvent and furtherwashing of the expanded starch with a non-aqueous water-soluble solventuntil at least 90 vol. % of the aqueous solvent added under step b isremoved. e. suspending the expanded starch in inert water-free organicsolvent, adding of a catalyst, adding of a fatty acid anhydride andeither i. keeping the mixture at a temperature and for a period of timesufficient to allow the formation of an esterified expanded starch, orii. treating the mixture in a micro-wave oven at 100-1000 W and for aperiod of 1 to 10 minutes sufficient to allow the formation of anesterified expanded starch; f. adding non-aqueous water-soluble solventto precipitate the esterified expanded starch, and drying of theesterified expanded starch; g. admixing a plasticizer to the esterifiedexpanded starch, allowing the formation of a plasticized esterifiedexpanded starch.
 23. Adhesive according to claim 22 wherein drying ofthe obtained expanded starch is performed in step d.
 24. Adhesiveaccording to claim 22 wherein the starch has an amylose content (w/w) ofat least 20%, preferably at least 40%, even more preferably at least50%, most preferably at least 60%.
 25. Adhesive according to claim 22wherein the gelatinized starch is obtained by hot aqueous solventtreatment at a temperature in the range of from 50° C. to 200° C., morepreferably of from 70° C. to 160° C., even more preferably of from 90°C. to 130° C.
 26. Adhesive according to claim 22 wherein retrogradationis induced by storing the hot aqueous solvent treated starch at atemperature below 25° C., preferably below 10° C., more preferably below5° C., but above −5° C., for at least 10 hours, preferably at least 24hours, more preferably at least 100 hours, more preferably at least 500hours.
 27. Adhesive according to claim 22 wherein the non-aqueouswater-soluble solvent is selected from the group consisting of ethanol,methanol, propanol, and butanol.
 28. Adhesive according to claim 22wherein the non-aqueous water-soluble solvent is added under step d) ina ratio of from 1 volumes non-aqueous watersoluble solvent to 5 volumehot aqueous solvent added in step b) to 5 volume nonaqueouswater-soluble solvent to 1 volume hot aqueous solvent added in step b).29. Adhesive according to claim 22 wherein after the further washing ofthe precipitated starch the precipitated starch is at least once washedwith the inert water-free organic solvent of step e), and omitting thedrying of the obtained expanded starch.
 30. Adhesive according to claim22 wherein the inert water-free organic solvent is selected from thegroup consisting of toluene, benzene, and xylene.
 31. Adhesive accordingto claim 22 wherein the catalyst is selected from the group consistingof amines, dimethylaminopyridine (DMAP), triethylamine, and pyridine,most preferably the catalyst is DMAP.
 32. Adhesive according to claim 22wherein the fatty acid anhydride is from C2 fatty acid anhydride to C12fatty acid anhydride, or mixtures thereof, preferably from C2 fatty acidanhydride to C6 fatty acid anhydride.
 33. Adhesive according to claim 22wherein the fatty acid anhydride is acetic anhydride.
 34. Adhesiveaccording to claim 22 wherein the plasticizer is selected from the groupconsisting of phthalate esters, dimethyl- and diethylsuccinate, glyceroltriacetate (triacetin), glycerol mono- and diacetate, glycerol mono-,di- and tripropionate, glycerol tributanoate (tributyrin), glycerolmono- and dibutanoate, glycerol mono-, di- and tristearate, and otherrelated glycerol esters, lactic acid esters, citric acid esters, adipicacid esters, stearic acid esters, oleic acid esters, ricinoleic acidesters, other fatty acid esters, glycerol, polycaprolactone,glyceryltrioleate, preferably the plasticizer is glycerol or glyceroltriacetate, most preferably the plasticizer is glycerol triacetate. 35.Adhesive according to claim 22 wherein the plasticizer is admixed in anamount from 10 to 40%, preferably from 15 to 35%, more preferably from20 to 30% by weight based on the esterified expanded starch. 36.Adhesive according to claim 22 wherein further flame-retardants,fillers, preservatives, binders, antimicrobial agents are admixed to theesterified expanded starch or the plasticized esterified expandedstarch.
 37. Method for preparing an hot aqueous solvent switchableadhesive, the method comprising the steps of a. providing starch; b.subjecting the starch to hot aqueous solvent treatment in order togelatinize the starch; c. treating the gelatinized starch to induceretrogradation in said gelatinized starch to obtain expanded starch; d.adding non-aqueous water-soluble solvent to precipitate the expandedstarch, substantially separating the precipitated expanded starch fromthe solvent and further washing of the expanded starch with anon-aqueous water-soluble solvent until at least 90 vol. % of theaqueous solvent added under step b is removed, e. suspending theexpanded starch in inert water-free organic solvent, adding of acatalyst, adding of a fatty acid anhydride and either i. keeping themixture at a temperature and for a period of time sufficient to allowthe formation of an esterified expanded starch, or ii. treating themixture in a micro-wave oven at 100-1000 W and for a period of 1 to 10minutes sufficient to allow the formation of an esterified expandedstarch; f. adding non-aqueous water-soluble solvent to precipitate theesterified expanded starch, and drying of the esterified expandedstarch; g. admixing a plasticizer to the esterified expanded starch,allowing the formation of a plasticized esterified expanded starch. 38.Method according to claim 37 wherein the drying of the obtained expandedstarch is performed in step d.
 39. Method according to claim 37 whereinthe starch has an amylose content (w/w) of at least 20%, preferably atleast 40%, even more preferably at least 50%, most preferably at least60%.
 40. Method according to claim 37 wherein the gelatinized starch isobtained by hot aqueous solvent treatment at a temperature in the rangeof from 50° C. to 200° C., more preferably of from 70° C. to 160° C.,even more preferably of from 90° C. to 130° C.
 41. Method according toclaim 37 wherein retrogradation is induced by storing the hot aqueoussolvent treated starch at a temperature below 25° C., preferably below10° C., more preferably below 5° C., but above −5° C., for at least 10hours, preferably at least 24 hours, more preferably at least 100 hours,more preferably at least 500 hours.
 42. Method according to claim 37wherein the non-aqueous water-soluble solvent is selected from the groupconsisting of ethanol, methanol, propanol, and butanol.
 43. Methodaccording to claim 37 wherein the non-aqueous water-soluble solvent isadded under step d) in a ratio of from 1 volumes non-aqueouswatersoluble solvent to 5 volume hot aqueous solvent added in step b) to5 volume nonaqueous water-soluble solvent to 1 volume hot aqueoussolvent added in step b).
 44. Method according to claim 37 wherein afterthe further washing of the precipitated starch the precipitated starchis at least once washed with the inert water-free organic solvent ofstep e), and omitting the drying of the obtained expanded starch. 45.Method according to claim 37 wherein the inert water-free organicsolvent is selected from the group consisting of toluene, benzene, andxylene.
 46. Method according to claim 37 wherein the catalyst isselected from the group consisting of amines, dimethylaminopyridine(DMAP), triethylamine, and pyridine, most preferably the catalyst isDMAP.
 47. Method according to claim 37 wherein the fatty acid anhydrideis from C2 fatty acid anhydride to C12 fatty acid anhydride, or mixturesthereof, preferably from C2 fatty acid anhydride to C6 fatty acidanhydride.
 48. Method according to claim 47 wherein the fatty acidanhydride is acetic anhydride.
 49. Method according to the claim 37wherein the plasticizer is selected from the group consisting ofphthalate esters, dimethyl- and diethylsuccinate, glycerol triacetate(triacetin), glycerol mono- and diacetate, glycerol mono-, di- andtripropionate, glycerol tributanoate (tributyrin), glycerol mono- anddibutanoate, glycerol mono-, di- and tristearate, and other relatedglycerol esters, lactic acid, esters, citric acid esters, adipic acidesters, stearic acid esters, oleic acid esters, ricinoleic acid esters,other fatty acid esters, glycerol, polycaprolactone, glyceryltrioleate,preferably the plasticizer is glycerol or glycerol triacetate, mostpreferably the plasticizer is glycerol triacetate.
 50. Method accordingto claim 37 wherein the plasticizer is admixed in an amount from 10 to40%, preferably from 15 to 35%, more preferably from 20 to 30% by weightbased on the esterified expanded starch.
 51. Method according to claim37 wherein further flame-retardants, fillers, preservatives, binders,antimicrobial agents are admixed to the esterified expanded starch orthe plasticized esterified expanded starch.
 52. Method of preparing arecyclable carpet or carpet tile comprising the steps of a. providing acarpet face layer b. providing a backing layer of one or more layers c.contacting a hot aqueous solvent switchable with the carpet face layerand the backing layer thereby adhering the carpet face layer to thebacking layer with the adhesive.
 53. Method for recycling components ofcarpet or carpet tiles comprising the steps of a. providing a recyclablecarpet or carpet tile obtained by the method according to claim 52; b.optionally reducing the size of the recyclable carpet or carpet tile; c.treating the recyclable carpet or carpet tile with an hot aqueoussolution and/or steam, at a temperature of at least 20° C., preferablyat least 30° C., preferably at least 70° C., more preferably at least90° C., for a period of time sufficient to allow the hot aqueous solventswitchable adhesive to detach (or de-adhere), or the adhesion of thesame to reduce; d. separating the carpet face layer from the backinglayer.
 54. A floor covering that at least comprises a carpet face layer,a backing layer, and a hot aqueous solvent switchable adhesive and whichadhesive directly or indirectly adheres the carpet face layer to thebacking layer.
 55. Use of a hot aqueous solvent switchable adhesive as aflame retardant.
 56. A carpet or carpet tile including a carpet facelayer and a backing layer comprising one or more layers with which thecarpet face layer is adhered by an adhesive, wherein said adhesive alsoacts as a flame retardant.
 57. A carpet or carpet tile according toclaim 56 wherein the adhesive is a hot aqueous solvent switchableadhesive comprising or essentially consisting of a plasticizedesterified expanded starch.